HIFU as an alternative treatment for symptomatic benign thyroid nodules

High-intensity focused ultrasound (HIFU) is a minimally invasive, high precision technique for the treatment of benign thyroid lesions in patients who either are not appropriate candidates for surgery or radioiodine therapy or who decline these treatments. Radiologists at the Department of Nuclear Medicine at University Hospital Frankfurt in Germany conducted a study to assess the effectiveness of HIFU in varying preablative nodules. They report that HIFU is an appropriate alternative treatment for benign nodules less than 3 milliliters (mL) in volume.

After a preablation assessment, HIFU treatment was performed on 15 patients with pathologically confirmed non-malignant nodules with a volume of 10 mL or less in size. A total of 19 nodules were treated in single HIF sessions at the German Center for Thermoablation of Thyroid Nodules. Eleven patients had nodules ranging 0.1-2.8 mL in volume, and eight patients had nodules ranging 3.5-7.7 mL. Nodule volume was assessed 90 days following the procedure. HIFU treatment was deemed a therapeutic success if nodule volume decreased by more than 50%, a success rate similar to radioiodine therapy.

Lead author Michael Sennert, MD, and colleagues reported in an Academic Radiology article that seven patients with nodules smaller than 3 mL achieved therapeutic success (64%) compared with had a median volume reduction of 64% compared to only three patients (38%) with larger nodules. They determined that a statistically significant negative correlation existed between volume shrinkage and nodule size.

The authors attributed treatment results to several factors. HIFU was used to ablate a region consisting of a single layer of lesions, which for larger nodules, volumes above and below the ablated regions were untreated. They suggest that two layers of lesions treated during a a single treatment session might resolve this. Movement in the neck caused by swallowing could also affect treatment, particularly for large nodules. Additionally when nodules are located close to sensitive structures such as the carotid artery or the trachea, treatment lesions will be automatically deselected. And when a nodule is located close to the skin, it might not be appropriate for HIFU treatment.

Newer HIFU systems in development might improve the success rate of treatments, the authors suggest. They also advocate its use as an alternative therapy. “Among the benefits of HIFU is the possibility of performing multiple treatment sessions. Considering the patients’ acceptance of HIFU treatment in general, multiple sessions are representing a very realistic therapy strategy. The additional treatment session approach should not be likely to be detrimental for the patient but might increase the efficiency dramatically,” they wrote. They hypothesize that remnant tissue existing after an initial treatment may become more vulnerable to further energy input during an additional session. But further research and development of additional safety procedures are needed before this becomes a common practice.

The HIFU treatment process

The treatment protocol utilized was developed by Huedazi Korkusuy, MD, of the Department of Nuclear Medicine.¹ The modality (Echopulse THC900888-H, Theraclion) incorporates two separate ultrasound systems in a single device. The imaging system has frequencies of 7.5 and 12 MHz, and the therapeutic system is driven at 3 MHz. The system automatically generates a sonication map, the targeted nodule and the marked structures around it. Sonications are delivered in a screw pattern while adjusting the energy level after each single sonication. Live sonication imaging shows the actual and planned images of the current delivery position, enabling the control of the therapeutic ultrasound probe focus location.

REFERENCES

1. Korkusuz H, Fehre N, Sennert M, et al. Volume reduction of benign thyroid nodules 3 months after a single treatment with high-intensity focused ultrasound (HIFU). J Ther Ultrasound. 2015 3: 4.
2. Sennert M, Happel C, Korkusuz Y, et al. Further Investigation on High-intensity Focused Ultrasound (HIFU): Effectiveness Related to Baseline Volumes. Acad Radiol. Published online August 23, 2017.